Method and device for battery charging and maintenance

ABSTRACT

A method and device is disclosed for charging and/or maintenance of lead-acid and alkaline accumulator batteries, allowing a charge, discharge, or recovery in control-conditioning cycles of these batteries. To increase efficiency of the battery recovery process, its charge is created by a reversible current in consecutive stages. Correction of the charging mode is provided based on voltage and temperature of the accumulator battery.

FIELD OF THE INVENTION

This invention relates to electro-technological methods and devices forthe maintenance of batteries, allowing to carry out the state control,regenerative charging, and cyclical recovery state of the battery.

BACKGROUND OF THE INVENTION

United States Patent Publication No. US 2004/0032247, by Dykeman,discloses a battery charging system that provides cyclic charging pulsesto a battery, wherein the charging pulse has a current component and avoltage component that varies between a quiescent voltage and a maximumvoltage. The system further comprises a battery monitoring circuitadapted to monitor one or more of the battery's parameters that respondto the charging pulses, and a control module that adjusts theconfiguration of the current component of the charging pulses tomaintain the voltage component in a range between the quiescent voltageand the maximum voltage in response to the monitored battery parameter.Charging and discharging pulses are alternated during the chargingcycle. The published patent application further discloses a temperaturesensing charger in which the charge discharge cycle is further regulatedbased upon the detected temperature of the battery. The maindisadvantage of this system is that it does not have a high recoveryefficiency for different battery states restored in the battery duringan initial period of operation.

U.S. Pat. No. 7,557,541, to Marinka-Tóth et al., discloses a chargingmethod by which the molecular movements in the cells of the rechargeablebattery can be accelerated. Through this process, the time necessary forthe chemical transformations and the time necessary for the full chargeitself can be reduced. In that patent, there are different chargingintervals inserted into the charging current, namely interval “a,” whichis a pulsed charging interval, followed by an interval “e,” which is acharging interval with a continuous charging current. That patentdiscloses using a short discharge interval prior to charging to increasea battery's charge take-up capacity. That patent also monitors theinternal resonance of the battery.

U.S. Pat. No. 6,856,118, to Lindqvist et al., discloses a batterycharging system using hardware, software, and microcomputers to controlthe charging of the battery. Per that disclosure, temperature andconductivity measurements are additionally taken to control the batterycharging. That patent regards a regeneration process for a battery,first to regenerate the chemical storage capacity, then to discharge thebattery, and finally to recharge the battery. That patent also disclosesa network and data storage system for the batteries to track theirmaintenance over time.

U.S. Pat. No. 6,504,344, to Adams et al., discloses a system fordetermining the health of a battery with multiple modules by measuringthe health of each module, performing a discharge of each module, andthen recharging each module, progressing from one module to the next.That disclosure takes into account the temperature of the battery orbattery modules when performing the health measurement, as well as thecharge and discharge cycles. That disclosure may offer the possibilityof individual equalization of the individual cells in the battery, butthat possibility requires a connection to the current lead battery as anadditional charge source. Modern batteries do not always have access tocurrent lead so the use of the method as disclosed by Adams et al. islimited to specific battery types.

In general, thyristors are unidirectional half-controlled electricwrenches. Thyristors can be forced open, and they close automatically ifthe current in its power circuit becomes less than the currentretention. The main advantage of thyristors is their high overloadcapacity: 10-30 fold excess of the limit (shock) on current workers. Theconsequence of this is the high reliability of the devices formed onthyristors. The main drawback of a thyristor, however, is the complexityof the forced locking.

To improve the reliability of the operation of thyristor devices,developers prefer to provide a natural lock thyristor (transitionsthrough zero voltage in the power supply). Torque control switchingthyristor systems provide pulse-phase control, which controls theswitching pulse delay with respect to the thyristor at a zero crossingin the mainstream voltage. This control principle is widely used inthyristor controlled rectifiers and inverters, i.e., the slave network.The latter term implies that the inverter thyristors provide naturalcommutation, i.e., they are locked under the influence of the mainstreamvoltage.

However, even when the battery charge is necessary to form a reversecurrent, i.e., to provide a consistently performing thyristor rectifierand inverter driven network, the design still cannot allow thesimultaneous operation of a thyristor rectifier and inverter, as thiswill lead to a short circuit in the network via the thyristors. Thus,such operation is possible only after the closing of one or the otherthyristor. The minimum pulse repetition period of the reverse current is70-80 ms (depending on the frequency of the current in the network),which is higher than the desired value in methods for battery chargingand maintenance. The present invention address this problem of theminimum pulse repetition period.

SUMMARY OF THE INVENTION

The claimed invention provides a battery in the process to introduce anadditional stage of alignment for batteries and where the reversecurrent equals the average values of the charging and dischargingcurrent. In this case, the conditions are created for the opening ofpores in the salt deposits on the electrodes of the battery and there isno battery power; that is, the alignment is performed between theindividual characteristics of the cells in the battery. The alignmentprocess will be accompanied by a decrease in the internal resistance ofthe battery, and the completion of the alignment process can be seen inthe stabilization of this resistance for 0.5 to 1.0 hour.

In some aspects, the present invention comprises a device for batterycharging and maintenance, comprising a terminal for an accumulatorbattery; the terminal having a positive side connected to a currentsensor; the terminal having a negative side connected to a ground; thecurrent sensor is electronically connected to a rectifier, saidrectifier comprising at least three rectifier thyristors, and aninverter, said inverter comprising at least three inverter thyristors;the rectifier and the inverter are connected to a transformer; thetransformer is connected to a power supply; and the terminal, theaccumulator battery, the inverter, the rectifier, and the current sensorare together electronically connected to a phase-pulse control system,thus forming a power supply network, said phase-pulse control systembeing configured to cause the power supply network to perform at leastone stage, said stage comprising: (1) forming a first pulse, said firstpulse being formed by the rectifier, said first pulse being synchronizedvia a front transition of a sinusoidal inter-phase voltage signal,wherein a first timer-counter controlling a first set of rectifierthyristors is synchronized by a first inter-phase voltage, wherein asecond timer-counter controlling a second set of rectifier thyristors issynchronized by a second inter-phase voltage, wherein a thirdtimer-counter controlling a third set of rectifier thyristors issynchronized by a third inter-phase voltage, (2) measuring a totalperiod (T) in the power supply network, said measuring being performedby one of said timer-counters, (3) causing a pause, said pause beingcaused by an end of an interval prior to a consecutive front transition,said pause further causing a closure of all rectifier thyristors, (4)forming a second pulse, said second pulse being formed by the inverter,said second pulse being synchronized at moments of inter-phase voltagepeaks in the power supply network, said inter-phase voltage peaks beingdetermined by adding an interval of T/4 to a given moment of a fronttransition of an inter-phase voltage, wherein a fourth timer-countercontrolling a first set of inverter thyristors is synchronized by thefirst inter-phase voltage, wherein a fifth timer-counter controlling asecond set of inverter thyristors is synchronized by the secondinter-phase voltage, wherein a sixth timer-counter controlling a thirdset of inverter thyristors is synchronized by the third inter-phasevoltage; and (5) repeating said first pulse, said pause, and said secondpulse.

In some aspects, the pause is 25-30 ms. In some aspects, the pause is30-70 ms. In some aspects, T is measured at least twice by saidtimer-counter and an average value of T is determined via a processorcoupled to said timer-counter. In some aspects, the phase-pulse controlsystem is in further electronic communication with a programmable logiccontroller. In some aspects, the programmable logic controller isfurther electronically connected to a human machine interface and to athermal monitor. In some aspects, the thermal monitor is furtherconnected to a thermal sensor, said thermal sensor being in contact withthe accumulator battery.

Also disclosed is a method for battery maintenance, comprisingconnecting a battery to a power supply network, performing at least onestage of charging, said at least one stage of charging comprising: (1)forming a first pulse, said first pulse being formed by a rectifier,said rectifier comprising at least three rectifier thyristors, saidfirst pulse being synchronized via a front transition of a sinusoidalinter-phase voltage signal, wherein a first timer-counter controlling afirst set of rectifier thyristors is synchronized by a first inter-phasevoltage, wherein a second timer-counter controlling a second set ofrectifier thyristors is synchronized by a second inter-phase voltage,wherein a third timer-counter controlling a third set of rectifierthyristors is synchronized by a third inter-phase voltage, (2) measuringa total period (T) in the power supply network, said measuring beingperformed by one of said timer-counters, (3) forming a second pulse,said second pulse being formed by an inverter, said inverter comprisingat least three inverter thyristors, said second pulse being synchronizedat moments of inter-phase voltage peaks in the power supply network,said inter-phase voltage peaks being determined by adding an interval ofT/4 to a given moment of a front transition of an inter-phase voltage,wherein a fourth timer-counter controlling a first set of inverterthyristors is synchronized by the first inter-phase voltage, wherein afifth timer-counter controlling a second set of inverter thyristors issynchronized by the second inter-phase voltage, wherein a sixthtimer-counter controlling a third set of inverter thyristors issynchronized by the third inter-phase voltage; (4) wherein a pauseoccurs between said first pulse and said second pulse, said pause beingcaused by an end of an interval prior to a consecutive front transition,said pause further causing a closure of all rectifier thyristors, (5)thus forming a first pulse-pause-second pulse signal for one or morestages of battery maintenance, and (6) repeating said first pulse, saidpause, and said second pulse.

In some aspects, the method comprises using only a pre-charge reversecurrent in a first stage. In some aspects, the method further comprisesa second stage of maintenance, said second stage employing a levelingreverse current for stabilizing an internal resistance of the battery.In some aspects, the method further comprises a third stage ofmaintenance, said third stage employing pulses of reverse current andfollowing said pulses of reverse current with a dead time. In someaspects, the method further comprises a fourth stage of maintenance,said fourth stage charging the battery using a reverse current. In someaspects, the third stage and the fourth stage are repeated at leastonce. In some aspects, the second stage lasts 0.5 to 1 hour.

In some aspects, a reverse current period is between 30-1000 ms induration. In some aspects, during stage 2 the average values of reversecurrent and forward current are equal. In some aspects, a reversecurrent period is between 30-1000 ms in duration. In some aspects,during stage 3 a duration of the powerful pulses of reverse current isbetween 180-1000 ms and a duration of the dead time is between 1000-5000ms. In some aspects, during stage 3 a ratio between reverse current andeither forward current or dead time is between 10:1-20:1. In someaspects, the method further comprises implementing a temperature controlof an electrolyte in the battery, comprising: monitoring the battery anddetermining if a battery temperature exceeds values of 35-50° C. duringmaintenance then reducing charge current by 30-50% and extending acharging stage for the battery accordingly; and monitoring the batteryand determining if a battery temperature exceeds values of 45-50° C.during maintenance then interrupting maintenance until the battery hascooled to a temperature of 25-35° C.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be discussed in further detail below withreference to the accompanying figures, in which:

FIG. 1 shows a functional diagram of the device for accumulator and/orbattery maintenance as described herein.

FIG. 2 shows the steps of the method for battery maintenance asdescribed herein.

FIG. 3 shows a more detailed version of the functional diagram shown inFIG. 1.

FIG. 4 shows an example of a formation of the output voltage pulses bythe rectifier thyristors according to one embodiment of the presentinvention.

FIG. 5 shows an example of a formation of the output voltage pulses bythe inverter thyristors according to one embodiment of the presentinvention.

FIG. 6 shows an example of a formation of the combined output voltagepulses of the forward-reverse current according to one embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In general, and based on the state of the art, the leading cause ofdeterioration of lead-acid battery parameters is the partialirreversible negative electrode sulfation, coupled with the partialirreversible hydration of the alkali. These processes are related to theovergrowth of salt deposits formed on the electrodes when the batterydischarges. If used in an alternating charge (i.e. reverse) current,then the recovery process in the salt precipitate is intensified andthere is a more complete electro-dissolution salt sediment and anincrease in associated battery electrode area recovery. At the same timewith the opening of pores in the battery with a partial capacity forwork will be charged and fully functioning batteries that will not leadto the equalization of the characteristics between the individualbatteries.

The present invention describes a charge-discharge means used formaintenance of lead-acid and alkaline accumulator batteries. One of thenovelties of the invention is the charge-discharge means used formaintenance of lead-acid and alkaline batteries and rechargeablebatteries. The term “charge-discharge means,” as used herein, is definedas including but not limited to the creation of forward and reversecurrents in a circuit, via the closing and opening of rectifierthyristors and inverter thyristors according to a periodic signal, whichin turn causes a flow of either a positive (forward) current or anegative (reverse) current, the thyristor(s) being connected in thecircuit with a battery to be charged and/or maintained.

The term “reverse(d) current,” as used herein, is defined as a currentapplied to the positive terminal of the battery to recharge the battery.

The present invention also describes a technological method for batterymaintenance that allows for the monitoring of battery condition,alignment characteristics of the cells in the battery, charge orrecovery of the battery, and a device for implementing the method.

Rechargeable battery maintenance is accomplished by alternating modes offull discharge control regimes and subsequent full charge. To equalizethe electrolyte concentration gradient in the cells of the batteryundergoing maintenance between the previous charge cycle and the nextdischarge cycle, there is generally a dead time of 10 minutes-180minutes.

Control discharge of the battery is performed using a stable andconstant-direction stream, I_(P) (see Table 1), to its full dischargevoltage, U_(P) (see Table 1). During the discharge process, the outputcapacity of the battery is measured to give average battery charge.

The method of charging the battery generally consists of 4 stages:pre-charge reversing current (1st stage), I_(Z1) (see Table 1), levelingreverse current (2nd stage), charging using powerful pulses of reversedcurrent followed by dead time (3rd stage), and charging using reversedcurrent (4th stage), I_(Z4) (see Table 1). If necessary, stages 3 and 4are repeated several times. Completion of stage 1, stage 3, and stage 4is carried out based on the charge time. Completion of stage 2 iscarried out to stabilize the internal resistance of the battery, takingapproximately 0.5 to 1 hours. At stages 1 and 4, the reversed currentperiod comprises about 30 milliseconds (ms) to 1,000 ms, and the ratioof the reversed current's average values is between 5:1 and 20:1.

During stage 2, the reverse current equals the average values of theforward and reverse components, each of which is calculated as thevalue, I_(Z1)/I_(Z2). The reverse current period is the same as in stage1.

In stage 3, the charge duration of the reverse current pulse is about180 ms to 1,000 ms, followed by a dead time of 1,000 ms to 5,000 ms. Theamplitudes of forward and reverse components are equal to I_(M) (seeTable 1), and the ratio of their mean values is between 10:1 and 20:1.

The battery maintenance process is completed after a full charge if: (1)there is no increase compared to previous cycle in the control dischargecapacity of the battery, or (2) if the last control discharge output was95-100% of the nominal capacity of the rated capacity of the batterybeing serviced.

During the process of battery maintenance, temperature control of theelectrolyte in the battery is implemented. If the battery temperatureexceeds values of 35-40° C. while charging, a single reduction incharging current of 30-50% is implemented and the charging stage isextended accordingly and proportionately. If the temperature range ofthe battery exceeds 45-50° C., then the process is interrupted until thebattery has cooled to a temperature of 25-35° C.

In the charge and discharge processes, the voltage across the batteryand the control group of battery cells is controlled. If their maximumpermitted voltage values, UM, are exceeded (see Table 1), then batterycharging is terminated. If, during the charge stage, the set voltagevalue, U_(C) (see Table 1), is exceeded, then charge current isdecreased 20-50% and stage phase duration is lengthened accordingly andproportionately.

TABLE 1 The values of technological parameters for serviceable types ofaccumulator batteries (where C_(N) = nominal capacity of the battery, inAmpere-hours; and n = quantity of accumulators in the battery): No ValueP/P Parameter Unit Lead Acid Type Alkaline Type 1 Discharge current,I_(P) A (0.025-0.2) · C_(N) (0.1-0.2) · C_(N) 2 The voltage of full B(1.75-1.8) · n (1-1.1) · n charge, U_(P) 3 The current first phase A(0.025-0.1) · C_(N) (0.05-0.25) · C_(N) of I_(Z1) charge 4 The amplitudeof the A (0.2-2) · C_(N) (0.25-4) · C_(N) current pulses of the thirdstage I_(M) charge 5 Fourth stage charge A (0.05-0.2) · C_(N) (0.1-0.25)· C_(N) current, I_(Z3) 6 Charge current B (2.4-2.65) · n (1.75-1.85) ·n compensation voltage, U_(K) 7 Termination voltage B (2.65-2.8) · n(1.85-1.9) · n U_(M) charge process

The device, implemented according to the claimed method of batterymaintenance, and performing the same steps as the claimed method ofbattery maintenance, comprises a power transformer (T) of the thyristorrectifier (R), the slave network thyristor inverter (I), an outputcurrent sensor (CS), a temperature sensor (TS), a system of phase-pulsethyristor control (PPCS), a programmable logic controller (PLC), anoperator human machine interface (HMI) panel, and a battery temperaturemonitor (TM).

The output current sensor is connected to the battery being serviced(AB), in which the individual control of temperature sensors (TS) areplaced on the batteries. Power is provided to the device from the mainAC power.

Formation of the battery discharge current is carried out in the slavenetwork thyristor inverter and the reverse current—due to alternate workthyristor rectifier and inverter driven network. These thyristors arecontrolled using the PPCS. The PPCS also provides digitization ofsignals from the output current sensor (CS) and the voltage across thebattery, and the PPCS controls the battery. The digitized data istransmitted to the PLC. The PPCS performs the function of stabilizingthe device's output current.

The algorithm of the proposed method of battery maintenance forbatteries in storage is implemented by the PLC. The PLC controls thethyristor phase-pulse control system. The TM collects data from thermalsensors in the accumulators of the battery undergoing maintenance andsends that data to the PLC.

The battery maintenance process operator controls the device using theHMI and is connected to the PLC.

FIG. 1 shows a functional diagram of the device according to the presentinvention. The core components and device blocks are labelled on thediagram: T—Transformer; R—Rectifier; I—Inverter; CS—Current Sensor;AB—Accumulator Battery; PPCS—Phase-Pulse Control System; HMI—HumanMachine Interface; PLC—Programmable Logic Controller; TM—ThermalMonitor; TS—Temperature Sensor.

FIG. 2 shows the steps of the method for battery maintenance accordingto the present invention: 10—connecting a battery to be maintained to abattery maintenance device; 11-stage 1—using a pre-charge reversecurrent; 12—stage 2 using a leveling reverse current for stabilizinginternal resistance of the battery; 13—stage 3 using powerful pulse(s)of reverse current and following the powerful pulse(s) of reversecurrent with dead time; 14—stage 4 charging the battery using reversecurrent; wherein each stage (1-4) involves either forward current ordead time alternating with reverse current; 15—determining a batterycharge amount via a battery charge control unit coupled to the battery.

If the battery charge control unit 15 indicates full charge, the processis determined as complete 16. Alternatively, 17, stages 3 and 4 may berepeated several times until the battery charge control unit 15indicates that the battery is fully recharged.

Stage 2 is preferably occurring for 0.5 hour to 1 hour.

During stages 1 and 4, a reverse current period is between 30 ms and1,000 ms. During stage 1 and stage 4, a ratio between (1) reversecurrent and (2) either forward current or dead time is preferablybetween 5:1 and 20:1.

During stage 2, the average values of reverse current and forwardcurrent are preferably equal. During stage 2, a reverse current periodis preferably between 30 ms and 1,000 ms.

During stage 3, a duration of the powerful pulses of reverse current ispreferably between 180 ms and 1,000 ms, and a duration of the dead timeis preferably between 1,000 and 5,000 ms. During stage 3, a ratiobetween (1) reverse current and (2) either forward current or dead timeis preferably between 10:1 and 20:1.

The completion of battery maintenance 16 occurs if: (1) there is noincrease compared to a previous cycle in a control discharge capacity ofthe battery, or (2) if a last control discharge output was between95-100% of a nominal capacity of a rated capacity of the battery beingserviced.

The method for battery maintenance preferably includes the step 18 ofimplementing temperature control of an electrolyte in the battery. Thisstep 18 includes monitoring the battery and determining if a batterytemperature exceeds values of 35-50° C. during maintenance, thenreducing the charge current by 30-50% and extending a charging stage forthe battery accordingly and proportionately. The step 18 also mayinclude monitoring the battery and determining if a battery temperatureexceeds values of 45-50° C. during maintenance, and then interruptingmaintenance until the battery has cooled to a temperature of 25-35° C.

The method implements voltage control of the battery by checking avoltage across the battery as compared to a control group of batterycells, determining if a threshold value is being exceeded, and thenterminating battery maintenance if the threshold value is in factexceeded.

In one embodiment, the method comprises voltage control of the batteryby checking a voltage across the battery as compared to a control groupof battery cells, determining if a threshold value is being exceeded,and then reducing the charge current 19 by 20-50% and lengthening stagephase duration accordingly and proportionately.

The primary PPCS is a programmable high-speed system on a chip (SoC; 1).The PPCS system comprises: six timer-counters, a vector interruptcontroller that supports at least three external interrupt inputs(Interrupt Input); an IO controller having at least twelve digitaloutputs (Digital Output); a 12-bit high-speed analog-digital converter(ADC) serving at least three analog inputs (ADC Input), and anasynchronous input-output serial port controller. In some embodiments,this controller comprises a Universal Synchronous/AsynchronousReceiver/Transmitter (USART).

The controller algorithm, implemented in SoC, enables formation of thealternating forward and reverse charge current pulses and formation ofdischarge current pulses. Furthermore, the algorithm providesindependent regulation of the average values of these currents andhigh-speed protection of the thyristors of the rectifier and inverterfrom overcurrent. This algorithm, it's effects, and its benefits, aredescribed in detail hereinbelow.

Synchronizing pulse generators 2 enable, in the PPCS, synchronization ofthe control signals by the thyristors of the rectifier (R) and inverter(I) via voltage in the power supply. Synchronization signals pass fromthe outputs of the synchronizing pulse generators 2 to the externalinterrupt inputs of the SoC 1, where during subroutine processing ofthese interrupts, the discharge synchronization of six timer-countersoccurs, providing control of the phase-shifts of control pulses of therectifier and inverter thyristors.

The thyristor control pulses of the rectifier from the SoC output passto the thyristor pulse generators 4, which generate pulses withparameters sufficient for opening thyristors; in addition, the thyristorpulse generators 4 provide a galvanic isolation between input and outputcircuits. Similar inverter thyristor pulse generators 5 are installed inthe control circuits of the inverter's thyristors.

The task of controlling the phase shift of control signals usingthyristors is calculated using inputted and actual current valuesthrough the battery (AB). Inputted values of output current and otherparameters for the required rectifier and inverter thyristor controlmode pass to the PPCS from the PLC via serial communication, which isensured by providing the SoC with USART, which has a network driver 3(e.g., RS-485) installed on its outputs.

Signals from the current sensor (CS) and voltage sensors on theaccumulator battery and accumulator control group pass to the PPCSinputs. In the PPCS, the signal from the current sensor is processed inthe input amplifier 6, and voltage signals are processed in thedifferential amplifiers 7. Similar signals pass from the output of theseamplifiers to the ADC SoC inputs, where the signals are digitized andaveraged. The values obtained from this processing step are transmittedto the PLC, and an actual current value is used in the PPCS forcontrolling current through the battery (AB).

FIG. 3 shows a more detailed diagram than that of FIG. 1. Namely, FIG. 3shows the following elements: TS—Thermal Sensor; 1—system on a chip(SoC); 2—synchronization pulse generators; 3—network driver (e.g.,RS-485); 4—thyristor control pulse generator for rectifier; 5—thyristorcontrol pulse generator for inverter; 6—input amplifier; 7—differentialinput voltage amplifiers.

Regarding FIGS. 4-6, a rectifier and inverter thyristor controlalgorithm is implemented in PPCS, allowing to form pulses of a constantcharge current (FIG. 4) or discharge current (FIG. 5), as well as theircyclic combinations—i.e., forward-reverse charge current, with a pause(FIG. 6).

In general, FIG. 4 explains the formation of the output pulses ofvoltage of the rectifier thyristors. FIG. 4 has the followingdesignations: V_(P)—supply voltage; V_(RS), V_(ST), V_(TR)—linearvoltage of the three-phase power supply; V_(C)—control voltage;V₁-V₆—control voltage related to rectifier thyristors (FIG. 1); V_(AB),E_(AB)—voltage and efficiency of the battery; t—time; T—period of thesupply voltage; t_(c)—delay of the control pulses for rectifierthyristors.

In general, FIG. 5 explains the formation of the output voltage pulsefrom the inverter thyristors. Figure has the following designations:V_(P)—supply voltage; V_(RS), V_(ST), V_(TR)—linear voltage of thethree-phase power supply; V_(C)—control voltage; V₇-V₁₂—control voltageof the corresponding inverter thyristors (FIG. 1); V_(AB),E_(AB)—voltage and efficiency of the battery; t—time; T—period of thesupply voltage; t_(d)—delay of the control pulses for the inverterthyristor.

In general, FIG. 6 explains the formation of the output voltage ofreverse current pulses. FIG. 4 has the following designations:V_(P)—supply voltage; V_(RS), V_(ST), V_(TR)—linear voltage of thethree-phase power supply; V_(C)—control voltage; V_(en R)—priority ofthe pulses formation by the rectifier (FIG. 2). V_(en I)—priority of thepulses formation by the inverter (see FIG. 5). V_(AB), E_(AB)—voltageand efficiency of the battery; t—time; t_(R)—interval for the pulseformation by the rectifier; t_(I)—interval for the pulse formation bythe inverter.

To control the rectifier thyristor(s) in the SoC, three timer-countersare used, the synchronization (i.e., reset) of which is performed usinga transition from negative to positive values (front transitions) ofsinusoidal inter-phase (linear) voltages of the supply (top of FIG. 4).The timer-counter that controls V₁ and V₂ thyristors is synchronized byV_(TR) voltage; the timer-counter that controls V₃ and V₄ thyristors issynchronized by V_(RS); and the timer-counter that controls V₅ and V₆thyristors is synchronized by V_(ST). Such is shown via the dashed linescorresponding to each labeled thyristor signal (FIG. 4).

One of the timer counters described herein also serves for measuring, T,the voltage period in the power supply network. Taking this measurementseveral times and over time, this particular timer stores valueaccumulated, and averaging said values based on a larger number ofsamples. The resulting average value is the voltage period, T, in thepower supply network. For a desired value of the phase shift of thethyristor control signal on the SoC, the delay on the t_(C) thyristorsturning-on may be calculated, as well as the time moments, in order toenable or disable the thyristors based on the timer-counters. When thesecalculated values coincide with the values accumulated in thetimer-counters, the desired level of the thyristor control signal V_(C)is achieved (FIG. 4), and the sequence of voltage pulses V_(AB) outputsfrom the device and is sent to the battery.

The remaining three timer-counters are used to control the inverterthyristors. They are synchronized at moments of inter-phase voltagepeaks in the supply network. The moments of maxima (FIG. 5) ofinter-phase voltage are detained by the interval, T/4, relative to themoments of frontal transitions of the inter-phase voltage. For example,a timer-counter may be programmed to measure a period of T/4 after afrontal transition of an interphase voltage coupled to thattimer-counter; therefore, at the end of the period of T/4, which isinitiated by the frontal transition, the timer-counter may cause thethyristor to switch (i.e., the switch occurs at the moment of maxima ofthat particular interphase voltage, via the algorithm). Thetimer-counter that controls thyristors V₇ and V₈ is synchronized withthe voltage V_(TR), the timer-counter that controls thyristors V₉ andV₁₀ is synchronized with the voltage V_(TR), and the timer-counter thatcontrols thyristors V₁₁ and V₁₂ is synchronized with the voltage V_(ST).The control of the inverter thyristors is similar to the control ofrectifier thyristors.

The formation of pulses of forward-reverse currents as the combinedoutput of the device (FIG. 6) is carried out by sequential operation ofthe thyristors of the rectifier and the inverter. Pulses that controlthe rectifier thyristors are formed only at a high level of the V_(enR)signal, and pulses that control the inverter thyristors are formed onlyat a high level of the V_(enI) signal. The rectifier operation startswhen one of the inter-phase voltages crosses zero. The duration of thisinterval, t_(R), is always a multiple of the period of the voltage inthe supply network. After ending of the interval, t_(R), the inverteroperation interval, t_(I), starts after the next transition through zeroof one of the inter-phase voltages. This solution allows for creating aminimally adequate t_(W) pause to close all the thyristors of therectifier. The t_(I) interval ends only after the next zero crossing ofthe inter-phase voltage. Then, the rectifier operation interval beginsand thus the formation of the cycle of the forward-reverse currentpulses are repeated.

Thus, the present invention allows for creating forward-reverse currentpulses with a repetition period starting from one and a half periods ofvoltage in the supply network.

A 4-stage battery charging mode, in contrast to existing charging modes,allows for a second stage wherein an alignment of batterycharacteristics occurs. The characteristics of the battery are alignedby using an alternating current with a charge equal to the average pulseforward and reverse currents. It should be noted that the proposedalignment procedure is carried out without additional charge devices anddoes not require monitoring of the state of the battery or batteries.

In order to form a reverse charge current and discharge current pulses,the invention uses a thyristor inverter driven network that allows torecover the electrical energy delivered by the battery in the powersupply network. Due to this, the device does not contain elements whichmay scatter this energy, such as, e.g., power resistors.

Combining the functions of thyristor rectifier and inverter control,digitizing the instantaneous values of current through the battery, andcalculating instantaneous values and/or the mean values of the forwardand reverse charge and discharge currents, regulation and stabilizationof the current in a single system on a single SoC chip is achieved. Itis possible to increase the speed of the thyristor control system andits reliability, and improve the parameters of the current regulation. Anarrow pulse after a failure is the result of a side effect of anarrival of the front of the rectification signal of the rectifierV_(enR) (FIG. 4). This occurs at the moment of fulfilling the conditionsfor unlocking the rectifier thyristors, V₄ and V₅ (FIG. 2). Thepresently disclosed systems and devices allows, through the operation ofthe algorithm, for the generation of reverse pulses with a period of25-30 ms after a forward pulse.

The method for battery maintenance further implementing voltage controlof the battery by checking a voltage across the battery and a controlgroup of battery cells and determining if a threshold value is beingexceeded then terminating battery maintenance.

The method for battery maintenance further implementing voltage controlof the battery by checking a voltage across the battery and a controlgroup of battery cells and determining if a threshold value is beingexceeded then reducing charge current by 20-50% and lengthening stagephase duration accordingly.

The method of battery maintenance, wherein a reverse current period isbetween 30-1000 ms in duration. The method of battery maintenance,wherein during stage 2 the average values of reverse current and forwardcurrent are equal. The method of battery maintenance, wherein duringstage 2 wherein a reverse current period is between 30-1000 ms induration. The method for battery maintenance, wherein during stage 3 aduration of the powerful pulses of reverse current is between 180-1000ms and a duration of the dead time is between 1000-5000 ms. The methodfor battery maintenance, wherein during stage 3 a ratio between reversecurrent and either forward current or dead time is between 10:1-20:1.The method for battery maintenance, further implementing a temperaturecontrol of an electrolyte in the battery, comprising: (1) monitoring thebattery and determining if a battery temperature exceeds values of35-50° C. during maintenance then reducing charge current by 30-50% andextending a charging stage for the battery accordingly; and (2)monitoring the battery and determining if a battery temperature exceedsvalues of 45-50° C. during maintenance then interrupting maintenanceuntil the battery has cooled to a temperature of 25-35° C.

The description of a preferred embodiment of the invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formsdisclosed. Obviously, many modifications and variations will be apparentto practitioners skilled in this art. It is intended that the scope ofthe invention be defined by the following claims and their equivalents.

Moreover, the words “example” or “exemplary” are used herein to meanserving as an example, instance, or illustration. Any aspect or designdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects or designs. Rather, use ofthe words “example” or “exemplary” is intended to present concepts in aconcrete fashion. As used in this application, the term “or” is intendedto mean an inclusive “or” rather than an exclusive “or”. That is, unlessspecified otherwise, or clear from context, “X employs A or B” isintended to mean any of the natural inclusive permutations. That is, ifX employs A; X employs B; or X employs both A and B, then “X employs Aor B” is satisfied under any of the foregoing instances. In addition,the articles “a” and “an” as used in this application and the appendedclaims should generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform.

What is claimed is:
 1. A device for battery charging and maintenance,comprising: a terminal for an accumulator battery; the terminal having apositive side connected to a current sensor; the terminal having anegative side connected to a ground; the current sensor iselectronically connected to a rectifier, said rectifier comprising atleast three rectifier thyristors, and an inverter, said invertercomprising at least three inverter thyristors; the rectifier and theinverter are connected to a transformer; the transformer is connected toa power supply; and the terminal, the accumulator battery, the inverter,the rectifier, and the current sensor are together electronicallyconnected to a phase-pulse control system, thus forming a power supplynetwork, said phase-pulse control system being configured to cause thepower supply network to perform at least one stage, said stagecomprising: forming a first pulse, said first pulse being formed by therectifier, said first pulse being synchronized via a front transition ofa sinusoidal inter-phase voltage signal, wherein a first timer-countercontrolling a first set of rectifier thyristors is synchronized by afirst inter-phase voltage, wherein a second timer-counter controlling asecond set of rectifier thyristors is synchronized by a secondinter-phase voltage, wherein a third timer-counter controlling a thirdset of rectifier thyristors is synchronized by a third inter-phasevoltage, measuring a total period (T) in the power supply network, saidmeasuring being performed by one of said timer-counters, causing apause, said pause being caused by an end of an interval prior to aconsecutive front transition, said pause further causing a closure ofall rectifier thyristors, forming a second pulse, said second pulsebeing formed by the inverter, said second pulse being synchronized atmoments of inter-phase voltage peaks in the power supply network, saidinter-phase voltage peaks being determined by adding an interval of T/4to a given moment of a front transition of an inter-phase voltage,wherein a fourth timer-counter controlling a first set of inverterthyristors is synchronized by the first inter-phase voltage, wherein afifth timer-counter controlling a second set of inverter thyristors issynchronized by the second inter-phase voltage, wherein a sixthtimer-counter controlling a third set of inverter thyristors issynchronized by the third inter-phase voltage; and repeating said firstpulse, said pause, and said second pulse.
 2. The device of claim 1,wherein the pause is 25-30 ms.
 3. The device of claim 1, wherein thepause is 30-70 ms.
 4. The device of claim 1, wherein T is measured atleast twice by said timer-counter and an average value of T isdetermined via a processor coupled to said timer-counter.
 5. The deviceof claim 1, wherein the phase-pulse control system is in furtherelectronic communication with a programmable logic controller.
 6. Thedevice for battery maintenance of claim 5, wherein the programmablelogic controller is further electronically connected to a human machineinterface and to a thermal monitor.
 7. The device for batterymaintenance of claim 6, wherein the thermal monitor is further connectedto a thermal sensor, said thermal sensor being in contact with theaccumulator battery.
 8. A method for battery maintenance, comprising:connecting a battery to a power supply network, performing at least onestage of charging, said at least one stage of charging comprising:forming a first pulse, said first pulse being formed by a rectifier,said rectifier comprising at least three rectifier thyristors, saidfirst pulse being synchronized via a front transition of a sinusoidalinter-phase voltage signal, wherein a first timer-counter controlling afirst set of rectifier thyristors is synchronized by a first inter-phasevoltage, wherein a second timer-counter controlling a second set ofrectifier thyristors is synchronized by a second inter-phase voltage,wherein a third timer-counter controlling a third set of rectifierthyristors is synchronized by a third inter-phase voltage, measuring atotal period (T) in the power supply network, said measuring beingperformed by one of said timer-counters, forming a second pulse, saidsecond pulse being formed by an inverter, said inverter comprising atleast three inverter thyristors, said second pulse being synchronized atmoments of inter-phase voltage peaks in the power supply network, saidinter-phase voltage peaks being determined by adding an interval of T/4to a given moment of a front transition of an inter-phase voltage,wherein a fourth timer-counter controlling a first set of inverterthyristors is synchronized by the first inter-phase voltage, wherein afifth timer-counter controlling a second set of inverter thyristors issynchronized by the second inter-phase voltage, wherein a sixthtimer-counter controlling a third set of inverter thyristors issynchronized by the third inter-phase voltage; wherein a pause occursbetween said first pulse and said second pulse, said pause being causedby an end of an interval prior to a consecutive front transition, saidpause further causing a closure of all rectifier thyristors, thusforming a first pulse-pause-second pulse signal for one or more stagesof battery maintenance, and repeating said first pulse, said pause, andsaid second pulse.
 9. The method of claim 8, comprising using only apre-charge reverse current in a first stage.
 10. The method of claim 9,further comprising a second stage of maintenance, said second stageemploying a leveling reverse current for stabilizing an internalresistance of the battery.
 11. The method of claim 10, furthercomprising a third stage of maintenance, said third stage employingpulses of reverse current and following said pulses of reverse currentwith a dead time.
 12. The method of claim 11, further comprising afourth stage of maintenance, said fourth stage charging the batteryusing a reverse current.
 13. The method of claim 12, wherein the thirdstage and the fourth stage are repeated at least once.
 14. The method ofclaim 10, wherein the second stage lasts 0.5 to 1 hour.
 15. The methodof claim 12, wherein a reverse current period is between 30-1000 ms induration.
 16. The method of claim 12, wherein during the second stageaverage values of reverse current and forward current are equal.
 17. Themethod of claim 12, wherein during the second stage wherein a reversecurrent period is between 30-1000 ms in duration.
 18. The method ofclaim 12, wherein during the third stage a duration of powerful pulsesof reverse current is between 180-1000 ms and a duration of the deadtime is between 1000-5000 ms.
 19. The method of claim 12, wherein duringsaid third stage a ratio between reverse current and either forwardcurrent or dead time is between 10:1-20:1.
 20. The method for batterymaintenance of claim 1, further implementing a temperature control of anelectrolyte in the battery, comprising: a. monitoring the battery anddetermining if a battery temperature exceeds values of 35-50° C. duringmaintenance then reducing charge current by 30-50% and extending acharging stage for the battery accordingly; and b. monitoring thebattery and determining if a battery temperature exceeds values of45-50° C. during maintenance then interrupting maintenance until thebattery has cooled to a temperature of 25-35° C.